Acquired by ABC News(CHARLESTON, S.C.) -- A several-day sentencing hearing is underway to determine the fate of former North Charleston, South Carolina, police officer Michael Slager, who has pleaded guilty to a federal civil rights offense in the shooting death of unarmed black man Walter Scott.

Slager could face up to life in prison. The sentence is at the discretion of the judge.

Slager, who is white, went on trial for the murder of Scott, an unarmed black man, after a traffic stop on April 4, 2015, while Slager was an officer with North Charleston's police department. Witness video that surfaced shortly after the encounter appeared to show the moment Slager fatally shot Scott as he ran away. He was fired from the force after the shooting.

Slager was charged in South Carolina with murder and pleaded not guilty. During the murder trial, Slager's attorney said his client shot Scott because he was in fear for his life. In 2016, the case ended in a mistrial. The state retrial and federal trial were expected to take place this year, but instead, in May Slager pleaded guilty to violating Scott's civil rights in federal court, ending the federal case against him and also resolving the state charges that were pending after the mistrial.

The witness video was analyzed in court on Monday to detail approximately how far away Scott was when Slager's first shot and final eighth shot were fired. Five of the shots hit Scott with all of the bullets entering from behind, the Justice Department said. According to FBI expert Tony Imel, who testified Monday, Scott was 16 feet, 5 inches away at the time of the first shot and 37 feet, 5 inches away for the seventh shot. Scott's distance at the time of the final eighth shot was unclear, but it was greater than the seventh.

The day of the shooting, Slager stopped Scott’s car when he saw a brake light wasn't working, and during the stop, Scott fled on foot and Slager followed him.

Feiden Santana, the witness who filmed the shooting, told prosecutors in court Monday that he saw Scott running away, and by the time Santana caught up with Scott in an empty lot, Scott was already on the ground, facing the ground with Slager on top of him.

Santana told the prosecution he saw the officer trying to control Scott and he heard something electric, which was later revealed by police to be Slager deploying his Taser.

Santana said he never saw Scott punch Slager, fight with Slager or charge toward Slager.

After Scott got off the ground and tried to run, Santana said he heard gunshots.

Slager told Scott to put his hands on his back, according to Santana, who added that he never saw Scott move after the gunshots.

After Slager used his Taser and Scott fell to the ground, "Scott managed to get off of the ground and again run away," the Justice Department said.

The Justice Department said in a statement in May that, according to documents filed in connection with the guilty plea, Slager "willfully used deadly force on Walter Scott even though it was objectively unreasonable under the circumstances."

But defense attorney Andy Savage said in court Monday that he will illustrate during the hearing that Slager was only responding to Scott resisting arrest.